Put incremental code flushing behind a flag.

src/mark-compact.cc

Index: src/mark-compact.cc
diff --git a/src/mark-compact.cc b/src/mark-compact.cc
index 641293399e6297d6824c2d07ee1d0ecf6cddd91b..ebba22b44a875b01006d01f0fe790636775ed8bf 100644
--- a/src/mark-compact.cc
+++ b/src/mark-compact.cc
@@ -1471,6 +1471,11 @@ void MarkCompactCollector::PrepareThreadForCodeFlushing(Isolate* isolate,
 void MarkCompactCollector::PrepareForCodeFlushing() {
   ASSERT(heap() == Isolate::Current()->heap());
 
+  // Enable code flushing for non-incremental cycles.
+  if (FLAG_flush_code && !FLAG_flush_code_incrementally) {
+    EnableCodeFlushing(!was_marked_incrementally_);
+  }
+
   // If code flushing is disabled, there is no need to prepare for it.
   if (!is_code_flushing_enabled()) return;
 
@@ -2033,6 +2038,11 @@ void MarkCompactCollector::AfterMarking() {
   // Flush code from collected candidates.
   if (is_code_flushing_enabled()) {
     code_flusher_->ProcessCandidates();
+    // If incremental marker does not support code flushing, we need to
+    // disable it before incremental marking steps for next cycle.
+    if (FLAG_flush_code && !FLAG_flush_code_incrementally) {
+      EnableCodeFlushing(false);
+    }
   }
 
   if (!FLAG_watch_ic_patching) {
@@ -3607,6 +3617,13 @@ void MarkCompactCollector::SweepSpaces() {
 
 
 void MarkCompactCollector::EnableCodeFlushing(bool enable) {
+#ifdef ENABLE_DEBUGGER_SUPPORT
+  if (heap()->isolate()->debug()->IsLoaded() ||
+      heap()->isolate()->debug()->has_break_points()) {
+    enable = false;
+  }
+#endif
+
   if (enable) {
     if (code_flusher_ != NULL) return;
     code_flusher_ = new CodeFlusher(heap()->isolate());